We recently described a novel putative Ca(2+) channel gene, MTR1, which shows a high level of homology to the human TRPC7 gene and the melastatin 1 (MLSN1) gene, another Trp (transient receptor potential protein)-related gene whose transcript was found to be downregulated in metastatic melanomas. It maps to human chromosome band 11p15.5, which is associated with the Beckwith-Wiedemann syndrome and predisposition to a variety of neoplasias. Here we report the isolation and characterization of the murine orthologue Mtr1. The chromosomal localization on distal chromosome 7 places it in a cluster of imprinted genes, flanked by the previously described Tapa1 and Kcnq1 genes. The Mtr1 gene encodes a 4.4-kb transcript, present in a variety of fetal and adult tissues. The putative open reading frame consists of 24 exons, encoding 1158 amino acids. Transmembrane prediction algorithms indicate the presence of six membrane-spanning domains in the proposed protein. Imprinting analysis, using RT-PCR on RNA from reciprocal mouse crosses harboring a sequence polymorphism, revealed biallelic expression of Mtr1 transcripts at all stages and tissues examined.